The present invention relates to a lead frame such that the lead frame is exposed on the bottom surface after it is encapsulated in a resin, and a method for fabricating a resin-encapsulated semiconductor device that can be surface-mounted on a substrate, using such a lead frame.
In recent years, there is an increasing demand for high-density mounting of semiconductor elements in order to realize smaller electronic devices with higher functionalities. Accordingly, the overall size and the thickness of a resin-encapsulated semiconductor device (a device obtained by integrally encapsulating a semiconductor chip and leads in a resin mold) have been quickly reduced. Moreover, various techniques have been developed in order to reduce the production cost and to increase the productivity.
A conventional method for fabricating a resin-encapsulated semiconductor device will now be described with reference to FIG. 11.
FIG. 11 illustrates a conventional method for fabricating a resin-encapsulated semiconductor device. More specifically, FIG. 11 is a cross-sectional view illustrating a step of separating a plurality of semiconductor devices resin-encapsulated onto a lead frame from one another. As illustrated in FIG. 11, a lead frame 101, on which a plurality of semiconductor devices 100 are individually encapsulated in a resin, is held on a dicing sheet 200, and then the lead frame 101 is cut by a cutting blade 201 along a cut region extending between adjacent semiconductor devices 100. A burr 101a (a rough edge remaining after cutting the lead frame 101) may be produced on the end surface (the cut surface) of the lead frame 101 after being cut by the cutting blade 201.
The burr 101a occurring on the bottom surface of the semiconductor device 100 is undesirable. If the semiconductor device 100 is a surface-mounted device in which the leads are exposed on the bottom surface thereof, the adherence between the semiconductor device 100 and the substrate on which it is mounted may be insufficient due to the burr 101a, thereby making the electrical connection therebetween imperfect.
While diamond powder, or the like, is typically applied on the cutting surface of the cutting blade 201, the cutting surface is likely to be loaded with metal powder as the cutting blade 201 is repeatedly used to cut the lead frame 101, which is made of a metal. Once the cutting blade 201 is loaded, the cutting process cannot be continued with the loaded cutting blade 201, and it is necessary to replace the loaded cutting blade 201 with a new blade. Such a replacement process reduces the productivity.
The present invention has been made to solve the these problems in the prior art, and has an object to reduce the burr occurring on the cut surface of a lead frame, thereby improving the quality of a resin-encapsulated semiconductor device while prolonging the life of a cutting blade, thus improving the productivity.
In order to achieve this object, the present invention provides a lead frame made of a metal and having cut regions along which the lead frame is cut into a plurality of semiconductor devices, wherein the cut regions are partially depressed to reduce the amount of metal existing along the cut regions. When fabricating a resin-encapsulated semiconductor device, the depressed portion of each cut region of the lead frame may be filled with an encapsulation resin.
Specifically, a first lead frame according to the present invention includes: an outer frame section; a plurality of chip mounting sections which are supported by the outer frame section and on which a plurality of semiconductor chips are mounted; lead sections surrounding the chip mounting sections; connecting sections for connecting and supporting the lead sections and the outer frame section with each other; and an encapsulation region in which the chip mounting sections are encapsulated together in an encapsulation resin, wherein an opening is provided in a plurality of regions of the outer frame section that are each located outside the encapsulation region and along an extension of one of the connecting sections.
In the first lead frame, an opening is provided in a plurality of regions of the outer frame section that are each located outside the encapsulation region and along an extension of one of the connecting sections. Therefore, when the lead frame is cut by a cutting blade along the connecting sections, the amount of the lead frame to be cut by the cutting blade is reduced in a portion of the outer frame section that is outside the encapsulation region. In this way, it is possible to reduce the occurrence of a burr of the lead frame and to suppress the loading of the cutting blade, thereby improving the quality of the resin-encapsulated semiconductor device while prolonging the life of the cutting blade, thus improving the productivity.
In the first lead frame, it is preferred that a width of the opening is greater than a thickness of cutting means for cutting the lead frame along the connecting sections. In this way, the cutting means does not contact the lead frame in the openings, thereby reliably suppressing the occurrence of a burr of the lead frame and the loading of the cutting means.
A second lead frame according to the present invention includes: an outer frame section; a plurality of chip mounting sections which are supported by the outer frame section and on which a plurality of semiconductor chips are mounted; lead sections surrounding the chip mounting sections; connecting sections for connecting and supporting the lead sections and the outer frame section with each other; and an encapsulation region in which the chip mounting sections are encapsulated together in an encapsulation resin, wherein a depressed portion is provided in a plurality of regions of the outer frame section that are each located outside the encapsulation region, on a reverse side of a runner section along which the encapsulation resin flows, and along an extension of one of the connecting sections.
In the second lead frame, a depressed portion is provided in a plurality of regions of the outer frame section that are each located outside the encapsulation region, on a reverse side of a runner section along which the encapsulation resin flows, and along an extension of one of the connecting sections. Therefore, when the lead frame is cut by a cutting blade along the connecting sections, the amount of the lead frame to be cut by the cutting blade is reduced in a portion of the outer frame section that is outside the encapsulation region. In this way, it is possible to reduce the occurrence of a burr of the lead frame and to suppress the loading of the cutting blade. In addition, the depressed portion may be filled with an encapsulation resin. Since an encapsulation resin is typically mixed with silica (silicon oxide) as a filler, there is provided a so-called xe2x80x9cdressing effectxe2x80x9d of recovering the cutting blade, etc., from a loaded state by the silica component mixed in the encapsulation resin. As a result, the occurrence of a burr is reduced, thereby improving the quality of the resin-encapsulated semiconductor device, while the life of the cutting blade can be prolonged by the dress effect provided by the silica component.
In the second lead frame, it is preferred that a width of the depressed portion is greater than a thickness of cutting means for cutting the lead frame along the connecting sections. In this way, the cutting means does not contact the lead frame in the depressed portions, and the cutting means instead contacts the encapsulation resin, thereby suppressing the occurrence of a burr of the lead frame while further improving the dressing effect on the cutting means.
In the first or second lead frame, it is preferred that each of the connecting sections includes a thinned portion whose thickness is smaller than a thickness of the outer frame section. In this way, the thickness of the encapsulation resin is increased above or below the connecting sections. Therefore, when the lead frame is cut by a cutting blade along the connecting sections, the amount of the lead frame to be cut by the cutting blade is reduced while the amount of the encapsulation resin to be cut by the cutting blade is increased, thereby reducing the burr of the lead frame and improving the dressing effect on the cutting blade.
In the first or second lead frame, it is preferred that another opening is provided in a plurality of regions of a peripheral portion of the encapsulation region that are each located along an extension of one of the connecting sections. In this way, since the other openings are located within the encapsulation region of the lead frame, the other openings are filled with the encapsulation resin, thereby further improving the dressing effect on the cutting blade.
In the first or second lead frame, it is preferred that a width of each of the connecting sections is smaller than a thickness of cutting means for cutting the lead frame along the connecting sections. In this way, when cutting the lead frame along the connecting sections into a plurality of devices, the cutting means can cut away the connecting sections completely. In addition, the alignment margin of the cutting means with respect to the connecting section is increased.
In such a case, it is further preferred that each of the connecting sections is chamfered near the lead sections, thereby reducing a thickness of the connecting section near the lead sections. This further reduces the amount of the lead frame to be cut by the cutting blade while increasing the amount of the encapsulation resin to be cut by the cutting blade, thereby reducing the burr of the lead frame and improving the dressing effect on the cutting blade.
A first method for fabricating a resin-encapsulated semiconductor device according to the present invention includes: a first step of providing a lead frame, the lead frame including: an outer frame section; a plurality of chip mounting sections which are supported by the outer frame section and on which a plurality of semiconductor chips are mounted; lead sections surrounding the chip mounting sections; connecting sections for connecting and supporting the lead sections and the outer frame section with each other; and an encapsulation region in which the chip mounting sections are encapsulated together in an encapsulation resin, wherein an opening is provided in a plurality of regions of the outer frame section that are each located outside the encapsulation region and along an extension of one of the connecting sections, and each of the connecting sections includes a thinned portion; a second step of mounting a plurality of semiconductor chips respectively on the chip mounting sections of the lead frame; a third step of electrically connecting each of the mounted semiconductor chips to the lead sections surrounding the semiconductor chip; a fourth step of integrally encapsulating the lead frame and semiconductor chips in an encapsulation resin; and a fifth step of cutting the encapsulated lead frame by using a cutting blade along the connecting sections so as to obtain a plurality of semiconductor devices each having at least one of the semiconductor chips included in the encapsulation resin, wherein the fourth step includes a step of encapsulating the lead frame and semiconductor chips so that a depression defined above or below each of the thinned portions of the lead frame is filled with the encapsulation resin.
The first method for fabricating a resin-encapsulated semiconductor device uses the first lead frame of the present invention, wherein each of the connecting sections includes a thinned portion, and the depression defined above or below the thinned portion is filled with an encapsulation resin. Thus, the thickness of the encapsulation resin is increased above or below the connecting sections. Therefore, the amount of the lead frame to be cut by the cutting blade is reduced while the amount of the encapsulation resin to be cut by the cutting blade is increased. As a result, the burr of the lead frame is reduced and the dressing effect on the cutting blade is improved, thereby improving the quality of the resin-encapsulated semiconductor device while prolonging the life of the cutting blade, thus improving the productivity.
A second method for fabricating a resin-encapsulated semiconductor device according to the present invention includes: a first step of providing a lead frame, the lead frame including: an outer frame section; a plurality of chip mounting sections which are supported by the outer frame section and on which a plurality of semiconductor chips are mounted; lead sections surrounding the chip mounting sections; connecting sections for connecting and supporting the lead sections and the outer frame section with each other; and an encapsulation region in which the chip mounting sections are encapsulated together in an encapsulation resin, wherein a depressed portion is provided in a plurality of regions of the outer frame section that are each located outside the encapsulation region, on a reverse side of a runner section along which the encapsulation resin flows, and along an extension of one of the connecting sections, and each of the connecting sections includes a thinned portion; a second step of mounting a plurality of semiconductor chips respectively on the chip mounting sections of the lead frame; a third step of electrically connecting each of the mounted semiconductor chips to the lead sections surrounding the semiconductor chip; a fourth step of integrally encapsulating the lead frame and semiconductor chips in an encapsulation resin; and a fifth step of cutting the encapsulated lead frame by using a cutting blade along the connecting sections so as to obtain a plurality of semiconductor devices each having at least one of the semiconductor chips included in the encapsulation resin, wherein the fourth step includes a step of encapsulating the lead frame and semiconductor chips so that a depression defined above or below each of the thinned portions of the lead frame is filled with the encapsulation resin.
The second method for fabricating a resin-encapsulated semiconductor device uses the second lead frame of the present invention, wherein each of the connecting sections includes a thinned portion, and the depression defined above or below the thinned portion is filled with an encapsulation resin. As a result, the second method for fabricating a resin-encapsulated semiconductor device of the present invention also provides effects as those provided by the first method of the present invention.
A third method for fabricating a resin-encapsulated semiconductor device according to the present invention includes: a first step of providing a lead frame, the lead frame including: an outer frame section; a plurality of chip mounting sections which are supported by the outer frame section and on which a plurality of semiconductor chips are mounted; lead sections surrounding the chip mounting sections; connecting sections for connecting and supporting the lead sections and the outer frame section with each other; and an encapsulation region in which the chip mounting sections are encapsulated together in an encapsulation resin, wherein a depressed portion is provided in a plurality of regions of the outer frame section that are each located outside the encapsulation region, on a reverse side of a runner section along which the encapsulation resin flows, and along an extension of one of the connecting sections; a second step of mounting a plurality of semiconductor chips respectively on the chip mounting sections of the lead frame; a third step of electrically connecting each of the mounted semiconductor chips to the lead sections surrounding the semiconductor chip; a fourth step of integrally encapsulating the lead frame and semiconductor chips in an encapsulation resin; and a fifth step of cutting the encapsulated lead frame by using a cutting blade along the connecting sections so as to obtain a plurality of semiconductor devices each having at least one of the semiconductor chips included in the encapsulation resin, wherein the fourth step includes a step of encapsulating the lead frame and semiconductor chips so that the depressed portions of the lead frame are not filled with the encapsulation resin.
The third method for fabricating a resin-encapsulated semiconductor device uses the second lead frame of the present invention, whereby the amount of the lead frame to be cut by the cutting means is reduced. As a result, the burr of the lead frame is reduced and the loading of the cutting means is reduced, thereby improving the quality of the resin-encapsulated semiconductor device while prolonging the life of the cutting blade, thus improving the productivity. Moreover, since the depressed portions provided in the runner section are not filled with the encapsulation resin, the depressed portions can be structurally simplified.
A fourth method for fabricating a resin-encapsulated semiconductor device according to the present invention includes: a first step of providing a lead frame, the lead frame including: an outer frame section; a plurality of chip mounting sections which are supported by the outer frame section and on which a plurality of semiconductor chips are mounted; lead sections surrounding the chip mounting sections; connecting sections for connecting and supporting the lead sections and the outer frame section with each other; and an encapsulation region in which the chip mounting sections are encapsulated together in an encapsulation resin, wherein a depressed portion is provided in a plurality of regions of the outer frame section that are each located outside the encapsulation region, on a reverse side of a runner section along which the encapsulation resin flows, and along an extension of one of the connecting sections; a second step of mounting a plurality of semiconductor chips respectively on the chip mounting sections of the lead frame; a third step of electrically connecting each of the mounted semiconductor chips to the lead sections surrounding the semiconductor chip; a fourth step of integrally encapsulating the lead frame and semiconductor chips in an encapsulation resin; and a fifth step of cutting the encapsulated lead frame by using a cutting blade along the connecting sections so as to obtain a plurality of semiconductor devices each having at least one of the semiconductor chips included in the encapsulation resin, wherein the fourth step includes a step of encapsulating the lead frame and semiconductor chips so that the depressed portions of the lead frame are filled with the encapsulation resin.
The fourth method for fabricating a resin-encapsulated semiconductor device uses the second lead frame of the present invention, wherein the depressed portions of the lead frame are filled with the encapsulation resin. Therefore, the amount of the lead frame to be cut by the cutting means is reduced while the amount of the encapsulation resin to be cut by the cutting means is increased. As a result, the burr of the lead frame is reduced and the dressing effect on the cutting blade is improved, thereby improving the quality of the resin-encapsulated semiconductor device while prolonging the life of the cutting blade, thus improving the productivity.